The individual sounds that make up words are called phonemes. They’re the smallest unit of sound that can change the meaning of a word.
If you take the word “mat” and replace the /m/ phoneme with the /r/ phoneme, you get the word “rat.” Then you can replace the /t/ phoneme with the /g/ phoneme to get another new word, “rag.”
Ear Training is really all about building phonemic awareness, also known as sound awareness, so we can hear the sometimes subtle differences between words.
Solo Letter Sounds are phonemes represented by the 26 letters of the alphabet, but phonemes aren’t always represented by one letter exclusively. For example, the “eɪ” (a) phoneme can be represented by just the letter “a,” but it can also be represented by a pair of letters like “ay” as in “say” or even a cluster of letters like “eigh” as in “neighbor.”
Fun fact: not all languages share the same phonemes. That's one reason some languages are more difficult to learn than others. It’s a lot harder to learn a new language when it has lots of sounds you’re not used to hearing or saying.